Here are some parody songs that I find very funny...
Shakira - "Whatever, Don't Matter" (Shake Your Money Maker)
Shakira - "Translation" (Subtitles Required)
Shakira - "Whenever, Whatever"
Britney Spears featuring Madonna - "Me Against Madonna" (In My Zone)
Christina Aguilera - "Virginal" (From the CD: Ho No Mo')
Nelly Furtado & Timbaland - "Syphilis Girl"
Katy Perry - "I Kicked a Girl" (Warning: Domestic Violence!)
Eminem - "What's on TV"
The others listed here were removed from YouTube... too bad... they were so funny...